A storage facility is a facility primarily used for storage of goods for commercial purposes, such as a warehouse. The storage is generally intended to be temporary, as such goods ultimately may be intended for a retailer, consumer or customer, distributor, transporter or other subsequent receiver. A warehouse can be a standalone facility, or can be part of a multi-use facility. Thousands of types of items can be stored in a typical warehouse. The items can be small or large, individual or bulk. It is common to load items on a pallet for transportation, and the warehouse may use pallets as a manner of internally transporting and storing items.
A well-run warehouse is well-organized and maintains an accurate inventory of goods. Goods can come and go frequently, throughout the day, in a warehouse. In fact, some large and very busy warehouses work three shifts, continually moving goods throughout the warehouse as they are received or needed to fulfill orders. Shipping and receiving areas, which may be the same area, are the location(s) in the warehouse where large trucks pick-up and drop-off goods. The warehouse can also include a staging area—as an intermediate area between shipping and receiving and storage aisles within the warehouse where the goods are stored. The staging area, for example, can be used for confirming that all items on the shipping manifest were received in acceptable condition. The staging area can also be used to build orders and pallets to fulfill orders that are to be shipped.
Goods in a warehouse tend to be moved in one of two ways, either by pallet or by cart (or trailer). A pallet requires a pallet transport for movement, such as a pallet jack, pallet truck, forklift, or stacker. A stacker is a piece of equipment that is similar to a fork lift, but can raise the pallet to significantly greater heights, e.g., for loading a pallet on a warehouse shelf. A cart requires a tugger (or “tow tractor”), which enables a user to pull the cart from place to place.
A pallet transport can be manual or motorized. A traditional pallet jack is a manually operated piece of equipment, as is a traditional stacker. When a pallet transport is motorized, it can take the form of a powered pallet jack, pallet truck, or forklift (or lift truck). A motorized stacker is referred to as a power stacker. A motorized pallet jack is referred to as a powered pallet jack, which an operator cannot ride, but walks beside. A pallet truck is similar to a powered pallet jack, but includes a place for an operator to stand.
As with motorized pallet transports, a tugger can be in the form of a drivable vehicle or in the form of a powered vehicle along the side of which the operator walks. In either form, a tugger includes a hitch that engages with a companion part on the cart, such as a sturdy and rigid ring or loop.
Automatic guided vehicle (AGV) forms of pallet trucks and powered tuggers exist. An AGV is a mobile robot that follows markers or wires in the floor, or uses vision or lasers to make its way without direct or remote control by an operator. They are most often used in industrial applications to move materials around a manufacturing facility or a warehouse, such as in the case of AGV forklifts and AGV tuggers.
FIG. 1 is a simplified diagram of a storage facility 100 in the form of a warehouse. Warehouses can range in size, e.g., a large warehouse can be 100,000 square feet or more. Warehouse 100 includes a shipping & receiving area 110 and a staging area 112. A loading dock may be provided, where goods can be loaded on and unloaded from trucks 116. In the staging area, pallets 114 are shown, and may be loaded with warehouse goods to fulfill an order. When a pallet 114 is loaded with goods, it can remain in the staging area 112 until it is ready for loading on a truck 116. In which case, the pallet 114 is moved to the shipping & receiving area 110 and then onto the truck 116.
Warehouse 100 includes a plurality of aisles and storage spaces (collectively aisles 120) where the goods are intended to be stored in an orderly manner. Additionally, zones can be defined in a warehouse—as a means for categorizing areas within a warehouse. A zone can be defined for an aisle, group of aisles, portion of an aisle, or various combinations thereof. In FIG. 1, several zones are defined, including zones A-E.
When one or more orders is to be filled, a “pick list” is generated, which tells an order selector (or picker) which aisles to go to and which goods to pick. Pallet transports or tuggers and carts (collectively pallet transport 130) are sent through warehouse 100 with the order selector to “pick” cases, totes, cartons, or other forms of containers of goods (collectively “cases” herein). A “tote” is a container that is used to fill an order on a piece-by-piece basis, where the pieces are individual goods or groupings of relatively small goods. The goods are arranged in aisles 120, and the same goods are arranged as a “pick face.” A “pick face” is a location, usually a two-dimensional facing or area, in a warehouse or stock area that is designated for the storage of one or more products and is accessible by an order selector for order filling. The cases are loaded on pallet transport 130 and brought to either the staging area 112 or shipping & receiving area 110.
FIG. 2 is a block diagram of a front view of an aisle and pick faces that can exist in aisle 120. In this view, four pick faces are shown, i.e., pick faces 0, 1, 5, and 6. Pick faces 0 and 1 are located on a shelf and pick faces 5 and 6 are at ground level. Each pick face is defined for a certain product. For example, pick face 0 shows 6 cases of the same product in FIG. 2.
There are different approaches to arranging products in a warehouse, which is referred to as “slotting.” Slotting is viewed by many to be the key to the efficiency of the warehouse operation, where the highest possible “pick rates” are desired. Generally speaking, “pick rate” means the number of cases or units picked per unit of time, e.g., cases per hour.
One common approach to slotting products is to use item velocity. Generally, the more popular a product is, the higher its item velocity—the faster or more frequently it moves in and out of the warehouse. When slotting by item velocity, it is typical to keep the products with the highest item velocities in zones closest to the shipping & receiving 110 area (or staging area 112). Meanwhile, items with the lowest item velocities tend to be in zones furthest away. Slotting by item velocity can reduce travel time within a warehouse when filling orders. Reducing travel time is an important factor in increasing pick rates—so it is considered quite advantageous to slot by item velocity.
Another way to slot products in a warehouse is by product categories—grocery stores tend to use this approach. For example, paper products may be a product category. One or more product categories may exist within a zone. To increase efficiency with this type of product slotting, it may be advantageous to pick all products from a category that are needed to fill multiple orders—and then put the orders together in the staging area 112.
There are many different methods for filling the order. The method chosen will typically depend on the way the products are slotted and whether or not cases are being picked versus individual products, e.g., a case of aspirin versus 12 bottles of aspirin. Some of the most common order picking methods are:                Single order picking—Each order selector selects a customer order and picks it to completion.        Batch picking—An order selector fills several orders at a time in order to reduce the amount of time spent traveling.        Pick and pass—Each order selector concentrates on his own area or zone and orders pass (mechanically or manually) from one order selector to the next.        Zone picking with aggregation on the shipping dock—Different zones send one or more cases to shipping for each order, and the cases from each zone are palletized together on the shipping dock.        Zone picking with aggregation at packing—Each zone sends one or more totes to a packing area (e.g., staging 112 in FIG. 1) with its portion of the order. At packing, all totes for an order are consolidated, and outbound cartons (e.g., boxes) are packed with the goods from the totes for a particular order.        Zone picking without aggregation—Each zone fills its carton for the order, and these are sent directly to the shipping trailer.        Unit sortation—Order selectors pull batches of product from their zones that are then sorted to the order by a tilt tray or cross-belt sorter.        
The appropriateness of a particular order filling method will also depend on its impact on pick rates. The higher the overall pick rate, the more efficient and cost effective the warehouse.
Referring again to FIG. 1, a warehouse management system, or WMS, 140 is a key part of the supply chain and primarily aims to control the movement and storage of goods within warehouse 100. The WMS can process transactions associated with the movement of goods into, out of, and within the warehouse, including shipping, receiving, putaway and picking. “Putaway” generally refers to moving goods into the warehouse or storage area at their designated storage locations, e.g., zones and pick faces.
The WMS can provide a set of computerized procedures to handle the tracking and management of goods at a warehouse, model and manage the logical representation of the physical storage facilities (e.g. racking etc.), and enable a seamless link to order processing and logistics management in order to pick, pack and ship product out of the warehouse. Warehouse management systems can be standalone systems, or modules of an enterprise resource management system or supply chain execution suite. Orders can be electronically received by a WMS or manually input. Pick lists can be automatically or manually generated from the order, which can include route optimization performed by the WMS.
When picking cases to fill orders, it is typical to use pallet transports 130 that are navigated through the warehouse 100 to pick faces within zones to retrieve the necessary product cases. When doing so, the pallet transport 130 is navigated under the control of the order selector. That is, the order selector looks at a first/next item on a pick list, which indicates the aisle, pick face, and (optionally) zone where the corresponding product is located. The order selector drives the pallet transport to the pick face, and loads the appropriate number of cases on the pallet (or cart). This is done for each product on the pick list, until the order selector has worked completely through the pick list.
If the order selector is only picking for a particular zone, he can bring the pallet transport to the next zone and hand it off to the next order selector to continue working down the pick list. If the order selector is picking the complete pick list, then he can drive the pallet transport to the shipping & receiving area 110 or staging area 112 when the order is complete.